The importance of proper alignment of vehicle wheels is well recognized. In former years alignment apparatus was essentially mechanical. That type of apparatus responded upon physically doing something to the vehicle wheels. Later advances utilized light beams and charts, and in the last few years the apparatus has moved into electronics, combined with radiant energy and consoles equipped with meters, responsive to wheel position monitoring circuits.
It is important to the successful use of electronic alignment apparatus to know what circuits relate to which wheels. It is also important to be able to know, when switches are manipulated, that the circuits associated with the selected switch position are functional, as well as being the proper circuits for the particular alignment information sought.